1. Field of the Invention
The present invention relates to detergent formulations which are free of phosphates, zeolites and crystalline layered silicates and which contain biodegradable polymers as builders.
2. Discussion of the Background
In detergents, materials known as builders are required as ingredients, in addition to surfactants. The function of the detergent builders is predominantly to eliminate from the wash process the calcium and magnesium ions originating from the wash water or from the dirt by complexing, dispersing and sequestering and to support the washing action of the surfactants. The builders prevent deposition on the fabrics, reduce incrustation of the textiles and improve primary detergency.
In traditional detergent formulations, polyphosphates, which also have outstanding performance characteristics, were used as builders. However, the use of phosphates in detergents is ecologically undesirable, since the pollution of effluents with phosphates leads to eutrophication of surface waters and to the problems associated therewith.
Today, combinations of water-softening silicates, such as zeolites or crystalline layered silicates, and polymers containing carboxylate groups are often used as builders in powder detergents. In this system, the zeolites or the layered silicates act as ion exchangers and soften the washwater by binding calcium and magnesium ions. The efficiency of the washing powders is substantially increased by the addition of polycarboxylates as cobuilders. Such builder systems are described, for example, in the textbook by J. Falbe, Surfactants in Consumer Products, 1987, 262-265 and 286-290, in European Patent 0,025,551 and in Seifen-O/ le-Fette-Wachse, NO. 18, 714 (1990).
Although the zeolites or crystalline layered silicates contained in the above-mentioned agents are not a danger to the environment, they have the disadvantage of contributing to a substantial increase in the amount of sewage sludge. There have therefore already been attempts to eradicate the use of water-softening silicates in phosphate-free detergent powders.
German Offenlegungsschrift 3,930,791 describes phosphate and zeolite-free detergents which contain polycarboxylates, in particular copolymers of acrylic acid and maleic acid, as incrustation inhibitors. However, these polymer builder substances have a disadvantage due to their low biodegradability.
German Offenlegungsschrift 4,022,005 claims the combination of citrate and polycarboxylates as builders in zeolite-free fine detergents. The polymers used have molecular weights of 30,000-120,000 g/mol. Accordingly, they possess only low biodegradability and can only be mineralized in the wastewater treatment plant to a small extent.
There is a strong desire in the art to provide detergents which are both phosphate and zeolite-free and which combine the characteristic of excellent biodegradability, while maintain high levels of detergency and incrustation inhibition.